Positive effect of ulnar nerve fascicle transfer to musculocutaneous nerve seeded with allogeneic adipose tissue derived stem cells on nerve regeneration for repairing upper brachial plexus injury in a rat model: A preliminary study.

BACKGROUND: Traumatic peripheral nerve injury, with an annual incidence reported to be approximately 13-23 per 100,000 people, is a serious clinical condition that can often lead to significant functional impairment and permanent disability. Although nerve transfer has become increasingly popular in the treatment of brachial plexus injuries, satisfactory results cannot be obtained even with total nerve root transfer, especially after serious injuries. To overcome this problem, we hypothesize that the application of stem cells in conjunction with nerve transfer procedures may be a viable alternative to more aggressive treatments that do not result in adequate improvement. Similarly, some preliminary studies have shown that adipose stem cells combined with acellular nerve allograft provide promising results in the repair of brachial plexus injury. The purpose of this study was to assess the efficacy of combining adipose-derived stem cells with nerve transfer procedure in a rat brachial plexus injury model. METHODS: Twenty female Wistar rats weighing 300-350 g and aged 8-10 weeks were randomly divided into two groups: a nerve transfer group (NT group) and a nerve transfer combined adipose stem cell group (NT and ASC group). The upper brachial plexus injury model was established by gently avulsing the C5-C6 roots from the spinal cord with microforceps. A nerve transfer from the ulnar nerve to the musculocutaneous nerve (Oberlin procedure) was performed with or without seeded allogeneic adipose tissue-derived stem cells. Adipose tissue-derived stem cells at a rate of 2 × 106 cells were injected locally to the surface of the nerve transfer area with a 23-gauge needle. Immunohistochemistry (S100 and PGP 9.5 antibodies) and electrophysiological data were used to evaluate the effect of nerve repair 12 weeks after surgery. RESULTS: The mean latency was significantly longer in the NT group (2.0 ± 0.0 ms, 95% CI: 1.96-2.06) than in the NT and ASC group (1.7 ± 0.0 ms, 95% CI: 1.7-1.7) (p < .001). The mean peak value was higher in the NT group (1.7 ± 0.0 mV, 95% CI: 1.7-1.7) than in the NT and ASC group (1.7 ± 0.3 mV, 95% CI: 1.6-1.9) with no significant difference (p = .61). Although S100 and PGP 9.5 positive areas were observed in higher amounts in the NT and ASC group compared to the NT group, the differences were not statistically significant (p = .26 and .08, respectively). CONCLUSIONS: This study conducted on rats provides preliminary evidence that adipose-derived stem cells may have a positive effect on nerve transfer for the treatment of brachial plexus injury. Further studies with larger sample sizes and longer follow-up periods are needed to confirm these findings.

Protective vs. Therapeutic Effects of Mitochondria-Targeted Antioxidant MitoTEMPO on Rat Sciatic Nerve Crush Injury: A Comprehensive Electrophysiological Analysis.

Protective vs. Therapeutic Effects of Mitochondria-Targeted Antioxidant MitoTEMPO on Rat Sciatic Nerve Crush Injury: A Comprehensive Electrophysiological Analysis. Peripheral nerve injuries often result in long-lasting functional deficits, prompting the need for effective interventions. MitoTEMPO (2-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl) triphenylphosphonium chloride) is a mitochondria-targeted antioxidant that has shown protective and therapeutic effects against pathologies associated with reactive oxygen species. This study explores the utilization of MitoTEMPO as a therapeutic and protective agent for sciatic nerve crush injuries. By employing advanced mathematical approaches, the study seeks to comprehensively analyze nerve conduction parameters, nerve excitability, and the distribution of nerve conduction velocities to gauge the potential. Forty Wistar-Albino rats were randomly divided into following groups: (I) SHAM-animals subjected to sham operation and treated intraperitoneally (i.p.) with vehicle (bidistilled water) for 14 days; (II) CI (crush injury)-animals subjected to CI and treated with vehicle 14 days; (III) MiP-animals subjected to 7 days i.p. MitoTEMPO treatment before CI (0.7 mg/kg/day dissolved in vehicle) and, only vehicle for 7 days after CI, protective MitoTEMPO; and (IV) MiT-animals i.p. treated with only vehicle for 7 days before CI and 7 days with MitoTEMPO (0.7 mg/kg/day dissolved in vehicle) after CI, therapeutic MitoTEMPO. Nerve excitability parameters were measured, including rheobase and chronaxie, along with compound action potential (CAP) recordings. Advanced mathematical analyses were applied to CAP recordings to determine nerve conduction velocities and distribution patterns. The study revealed significant differences in nerve excitability parameters between groups. Nerve conduction velocity was notably reduced in the MiP and CI groups, whereas CAP area values were diminished in the MiP and CI groups compared to the MiT group. Furthermore, CAP velocity was lower in the MiP and CI groups, and maximum depolarization values were markedly lower in the MiP and CI groups compared to the SHAM group. The distribution of nerve conduction velocities indicated alterations in the composition of nerve fiber groups following crush injuries. In conclusion, postoperative MitoTEMPO administration demonstrated promising results in mitigating the detrimental effects of nerve crush injuries.

Abdominal Ischemia-Reperfusion Induced Cardiac Dysfunction Can Be Prevented by MitoTEMPO.

BACKGROUND: Cardiac dysfunction is secondary to acute mesenteric ischemia (AMI) and abdominal aortic aneurysms (AAA). The underlying cause of distant organ damage in the heart is the formation of oxidative stress caused by ischemia-reperfusion. In this study, we investigated the possible protective effects of a novel mitochondria-targeted antioxidant MitoTEMPO on contractile dysfunction and structural defects of the rat papillary muscle caused by abdominal ischemia-reperfusion (AIR). METHODS AND RESULTS: In the experiments, adult Wistar-Albino rats were used and animals were divided randomly into 3 groups; sham-operated group (SHAM), an IR group that had aortic cross-clamping for 1 h followed by 2 h reperfusion, and a third group that received protective 0.7 mg/kg/day MitoTEMPO injection for 28-day before IR. As a result, it was observed that MitoTEMPO injection had a protective effect on the mechanical activities and structural properties of the papillary muscle impaired by AIR. Our study also showed that AIR disrupted the contractile function of the papillary muscle for each stimulation frequency and post-potentiation responses tested. This is common for each measured and calculated mechanical parameter and MitoTEMPO injection showed its protective effects. CONCLUSION: Consequently, calcium homeostasis seems to be impaired by AIR, and MitoTEMPO may exert its protective effect through energy metabolism by directly targeting the mitochondria.

Can MitoTEMPO protect rat sciatic nerve against ischemia-reperfusion injury?

Abdominal ischemia-reperfusion (I/R) is known to cause both structural and functional damage to sciatic nerve which is related to the oxidative stress. We investigated the protective effects of mitochondria-targeted antioxidant (2-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl) triphenylphosphonium chloride (MitoTEMPO) on ischemia-reperfusion-induced nerve damage by using the conduction velocity distribution (CVD) calculations from in vitro compound nerve action potential (CNAP) recordings from rat sciatic nerve. Adult male Wistar albino rats were divided into three groups. The IR and IR + MT groups had aortic cross-clamping for 1 h followed by 2 h reperfusion, while SHAM group had the same procedure without cross-clamping. IR + MT group received 0.7 mg/kg/day MitoTEMPO injection for 28 days before I/R, while other groups received vehicle alone. Ischemia-reperfusion resulted in a significant decrease (p < .05) in maximum depolarizations (mV), areas (mV.ms), and maximum and minimum upstroke velocities (mV/ms) of CNAPs, while injection of MitoTEMPO showed a complete protective effect on these impairments. The histograms for CVD showed that I/R blocked the contribution of fast-conducting fibers (> 60 m/s). MitoTEMPO prevented that blockage and caused a shift in the CVD. Functional nerve damage caused by I/R can be prevented by MitoTEMPO, which can enter mitochondria, the main source of reactive oxygen species (ROS).

Axonal excitability and conduction alterations caused by levobupivacaine in rat.

In this study, effects of the long-acting amide-type local anesthetic levobupivacaine on axonal conduction and excitability parameters of the rat sciatic nerve were thoroughly examined both in vitro and in vivo. In order to deduce its effects on isolated nerve conduction, compound nerve action potential (CNAP) recordings were performed using the suction method over sciatic nerves of Wistar rats before and after administration of 0.05 % (1.7 mmol L-1) levobupivacaine. Levobupivacaine caused complete CNAP area and amplitude depression by blocking conduction in a time-dependent manner. To assess the influence of levobupivacaine on in vivo excitability properties, threshold-tracking (TT) protocols were performed at sciatic nerves of rats injected with perineural 0.05 % (1.7 mmol L-1) levobupivacaine or vehicle alone. Charge-duration TT results revealed that levobupivacaine increases the rheobase and decreases the strength-duration time constant, suggesting interference of the anesthetic with the opening of Na+ channels. Twenty and 40 % threshold electrotonus curves were found for both groups to follow the same paths, suggesting no significant effect of levobupivacaine on K+ channels for either the fastest or relatively slow conducting fibers. Current-threshold relationship results revealed no significant effect on axonal rectifying channels. However, according to the results of the recovery cycle protocol yielding the pattern of excitability changes following the impulse, potential deviation was found in the recovery characteristics of Na+ channels from the absolute refractory period. Consequently, conduction blockage caused by levobupivacaine may not be due to the passive (capacitive) properties of axon or the conductance of potassium channels but to the decrease in sodium channel conductance.

Electrophysiological alterations in diaphragm muscle caused by abdominal ischemia-reperfusion.

Ischemia-reperfusion injury is the major complication of abdominal aortic surgery, and it mainly affects the lower extremities and remote organs. In the present study, the electrophysiological alterations in diaphragm that underlie the post-operative respiratory dysfunction were investigated. Wistar Albino rats were randomly divided into two groups: SHAM (only laparotomy was performed) and IR (abdominal aorta was clamped for 30min and reperfused for 2h). Following the operational period diaphragm muscles were isolated and electrophysiological experiments were carried out in-vitro. 3nM Ryanodine application, Na+ and K+ current blockage (0.3mM 4-Aminopyridine and 127mM N-methyl-d-glukamine) experiments were also conducted to further reveal any alterations. Twitch and tetanic force were decreased significantly. Action potential overshoot, amplitude and area were increased while diaphragm muscle cells were found to be hyperpolarized significantly. Mechanical alterations were shown to be caused by deterioration of Ca++ homeostasis. At resting state, a decrease in persistent Na+ current was found. The reshaping of action potential, on the other hand, was shown to be due to altered kinetics of Na+ channels and delayed activation of voltage dependent K+ channels.

Dexmedetomidine augments the effect of lidocaine: power spectrum and nerve conduction velocity distribution study.

BACKGROUND: In this study, the individual and combined inhibitory effects of dexmedetomidine and lidocaine on the conduction group of isolated nerve were investigated by determining conduction velocity distribution (CVD) and power spectrum. METHODS: Electrophysiological compound action potential (CAP) recordings were conducted on isolated rat sciatic nerve before (Con) and 20 minutes after exposure to 1 mM lidocaine (Lido), 21pM dexmedetomidine (Dex) and their combination (Lido + Dex). Then for CVD, mathematical model and for power spectrum Fast Fourier analysis were conducted. RESULTS: Dexmedetomidine alone made no significant difference in shape and duration of CAPs as compared to Con, on the other hand lidocaine depresses amplitude and prolongs the duration of CAPs, but not more than combination of dexmedetomidine and lidocaine can do. Lidocaine caused a shift in the CVD histogram to relatively slower conducting group significantly while dexmedetomidine did not cause any significant change as compared to Control. Lidocaine, when combined with dexmedetomidine revealed a remarkable effect on the whole CVD histogram by causing almost complete blockage of fast conducting nerve fibers. The relative number of fibers in CVD is conserved for separate applications of anesthetics, but not for their combination. As in CVD, power spectrum shifted from higher to lower frequency region by lidocaine and significantly for lidocaine combined with dexmedetomidine application. Shifts for dexmedetomidine applied group were seen beggarly. CONCLUSIONS: We have concluded that dexmedetomidine alone did not influence nerve conduction, but when it is used with lidocaine it augments neural conduction blockage effect, especially on fast conducting nerve fibers.

An early diagnostic tool for diabetic neuropathy: conduction velocity distribution.

Diabetes is a metabolic disorder that affects much of the human population. As a secondary complication, diabetic neuropathy causes time-dependent damage to peripheral nerves. In this study, experimental diabetes was induced by streptozotocin (STZ; 50 mg/kg intraperitoneally) in rats. Diabetic animals were grouped into those with 2 or 4 weeks of diabetes, whereas a control group received only the STZ vehicle (0.1 M citrate). Sciatic nerves were dissected, and compound action potentials (CAPs) were recorded. Results deduced by conventional calculation carried less information when compared with conduction velocity distribution (CVD) obtained by a computer-based mathematical model. Using the conventional approach, statistically significant changes were first seen in the fourth week of diabetes, whereas results deduced by CVD measurement could be seen in the second week. Consequently, the CVD calculation provides more information for the early diagnosis of neuropathies compared with classical conduction velocity measurements.

Comparative effects of α lipoic acid and melatonin on cisplatin-induced neurotoxicity.

Cisplatin is a carcinogenic agent having important cytotoxic effects. Cisplatin treatment increases the levels of free oxygen radicals in neurologic tissues. We investigated the effects of alpha lipoic acid (ALA) and melatonin (MEL) on the electrophysiological parameters and on activities of nerve fibers having different conduction properties on cisplatin neurotoxicity. Neurotoxicity was induced by a single injection of 10 mg/kg intraperitoneal (ip) cisplatin. Supplementation was started 1 day before cisplatin injection with either 100 mg/kg/day ip ALA or 4 mg/kg/day ip MEL for 7 days. Compound action potentials were recorded from isolated sciatic nerves in vitro, and numerical analyses were conducted. Cisplatin-induced neurotoxicity resulted in a significant decrease (p <.05) in maximum depolarization (mV), areas (mV·ms), and maximum and minimum upstroke velocity values (mV/ms). Although these decrements were restored by ALA and MEL, ALA was found to be more effective. Conventional conduction velocity measurements and conduction velocity distribution histograms have shown that ALA supplementation can recover the effects of cisplatin while MEL cannot. The conduction velocity distribution histograms have shown that antioxidant supplementation results in a restoration on contribution of fast-conducting fibers (51.8-77.7 m/s), which is deteriorated by cisplatin. Consequently, ALA has more potential to make up for the deleterious effects of cisplatin-induced neurotoxicity.

Effect of tramadol on the rat sciatic nerve conduction: a numerical analysis and conduction velocity distribution study.

The aim of this study was to document the effect of tramadol as an opioid on individual fibers of rat sciatic nerve. To accomplish this objective, compound action potentials (CAPs) were recorded from isolated nerves treated with tramadol from five different concentration levels. Then recorded CAPs and the control group were analyzed by numerical methods namely Conduction Velocity Distribution (CVD) and Fast Fourier Transform (FFT). The results show that the area under CAP and the time derivative of CAP curves decreases, and the excitability of the nerve trunk falls as well (rheobase and chronaxie increases) with increasing tramadol concentration. CVD deduced by model study was divided into subgroups as SLOW (8-26 m/s), MODERATE (26-44 m/s), MEDIUM (44-60 m/s) and FAST (60-78 m/s). The decrement in percentage relative contribution of these conduction velocity groups starts with a concentration of 0.25 mM tramadol, especially in the subgroup named FAST. The power spectrum shifts from higher frequency region to lower frequency region as the tramadol concentration increases. These findings show that fast conducting fibers are more susceptible to tramadol than medium and moderate groups and tramadol possibly acts on channel activity rather than passive properties (such as space and time constant) of nerve fibers.

Coenzyme Q(10) and alpha-lipoic acid supplementation in diabetic rats: conduction velocity distributions.

Diabetic neuropathies are a family of nerve disorders caused by diabetes. Patients with diabetes can develop nerve problems at any time, but the longer a person has diabetes the greater the risk. This study aims to investigate diabetes- and coenzyme Q(10) (CoQ(10)) or alpha-lipoic acid (ALA) supplementation-induced changes in the conduction velocity (CV) distributions of rat sciatic nerve fibers. Sciatic nerve compound action potentials (CAPs) were recorded by suction electrode and CV distributions by the collision technique. Diabetes resulted in a significant increase in time to peak, rheobase and chronaxie values of these CAP waveforms, whereas the maximum depolarization, area, kinetics and CVs of both fast and slow nerve fiber groups were found to be decreased. Coenzyme Q(10) (CoQ(10)) supplementation was found to have some positive effect on the diabetes-induced alterations. CoQ(10) supplementation induced positive changes mainly in the area and fall-down phase of the kinetics of CAP waveforms, as well as rheobase, chronaxie and speed of the intermediately conducting groups ( approximately or equal to 40 m/s). alpha-Lipoic acid (ALA) supplementation did not produce statistically significant effects. This study has shown for the first time that diabetes induces a shift of actively contributing nerve fibers toward slower CVs, and supplementation with CoQ(10) not only stopped this shift but also tended to restore velocities toward those of the age-matched control group. In addition to its effects on mitochondrial alterations, these positive effects of CoQ10 on diabetic neuropathy can be attributed to its antioxidant activity.

Selenium-induced changes on rat sciatic nerve fibers: compound action potentials.

The nervous system, through its important role as a communication network, governs reactions to stimuli, processes information and generates elaborate patterns of signals to control complex behaviors. Although selenium (Se) was shown to have some beneficial effects in pathological conditions, it is still a toxic element with a fairly small therapeutic window. In this study, the direct effects of Se ranging from 10(-8) to 10(-4) M were tested on rat sciatic nerve preparations. The toxicity started at 10(-8) M and the degree of alterations was found to be dose-dependent. In between the measured parameters, total compound action potential area (Astart = 3.70 +/- 0.16 ms x mV and A(-8) M = 3.04 +/- 0.14 ms x mV) and maximum depolarization points (MDstart = 6.70 +/- 0.22 mV and MD(-8) M = 6.04 +/- 0.18 mV) were the first to be affected from 10(-8) M. Latencies and conduction velocity distribution measurements have shown that nerve fibers having intermediate conduction velocities (20-35 m/s) are the first to be affected from this toxicity. Despite the fact that the new claims concluded the positive effects of the administrations, it is evident that the dose of supplementation must be fine-tuned to avoid possible side effects.

Sexual dependency of rat sciatic nerve fiber conduction velocity distributions.

Gender differences, either with the structural or through with hormones, dictate how the corresponding organ or organ system responses to physiological signals. Current study aims to investigate gender dependent differences in conduction related parameters of rat sciatic nerve. Compound action potentials (CAP) were recorded via suction electrode whereas the conduction velocity distributions (CVD) were performed using the method known as collision technique in the literature. Studied CAP parameters, namely conduction velocities (CV), area of the CAPs and time required to reach the maximum depolarization (TP) have been found significantly different for female and male rats. Detailed analyses have shown that sex dependent differences were more remarkable in the right leg responses of female and male rats. Additionally, CVDs indicate that the number of fibers having CVs between 5-30 m/s is much more in male right sciatic nerve trunk when compared to age matched female rats. The present study, for the first time clearly shows that shift in the contribution of nerve fibers to lower CVs is the main causal of the sex dependent differences seen in rat sciatic nerve fibers.

Gender-dependent effects of selenite on the perfused rat heart: a toxicological study.

Gender differences are related to the manner in which the heart responds to chronic and acute stress conditions of physiological and pathological nature. Depending on dose, sodium selenite acts as an antioxidant proven to have beneficial effects in several pathological conditions G. Drasch, J. Schopfer, and G. N. Schrauzer, Selenium/cadmium ratios in human prostates: indicators of prostate cancer risk of smokers and nonsmokers, and relevance to the cancer protective effects of selenium, Biol. Trace Element Res. 103(2), 103-107 (2005); R. G. Kasseroller and G. N. Schrauzer, Treatment of secondary lymphedema of the arm with physical decongestive therapy and sodium selenite: a review, Am. J. Ther. 7(4), 273-279 (2000); G. N. Schrauzer, Anticarcinogenic effects of selenium, Cell. Mol. Life Sci. 57(13-14), 1864-1873 (2000); I. S. Palmer and O. E. Olson, Relative toxicities of selenite and selenate in the drinking water of rats, J. Nutr. 104(3), 306-314 (1974). To date, little is known about the gender-dependent direct effects of toxic doses of selenite on electrophysiology of the cardiovascular system H. A. Schroeder and M. Mitchener, Selenium and tellurium in rats: effect on growth, survival and tumors, J. Nutr. 101(11), 1531-1540 (1971); G. N. Schrauzer, The nutritional significance, metabolism and toxicology of selenomethionine, Adv. Food Nutr. Res. 47, 73-112 (2003). In the present study, the effects of in vitro toxic concentrations of sodium selenite ranging from 10-6 M to 10-3 M were tested on both male and female rat heart preparations. The toxic effects seen in an electrocardiogram and left ventricular pressure were dose and sex dependent at most of the tested concentrations. The present study clearly shows that at toxic doses, stress conditions are induced by selenite, resulting in genderdependent modifications of the heart function. This modification is more pronounced in the contraction cascade of female rats. Males, on the other hand, had been much more affected in excitation-related parameters.